Effects of okra (Abelmoschus esculentus L.) leaves, fruits and seeds extracts on European sea bass (Dicentrarchus labrax) leukocytes, and their cytotoxic, bactericidal and antioxidant properties

Okra, Abelmoschus esculentus L., is a popular vegetable crop with many bioactive compounds. The in vitro immunostimulant, cytotoxic, bactericidal and antioxidant activities of ethanolic extracts obtained from different parts of okra (leaves, fruits, and seeds) were studied. Phytochemical screening of hydroalcoholic extracts of okra leaves, fruits and seeds revealed a significant content of total phenols and flavonoids. Notable effects on the activities of leukocytes in the head kidney of European sea bass (Dicentrarchus labrax) (viability, phagocytic ability and capacity, and respiratory burst), as well as on peroxidase leukocyte contents were detected after incubation for 24 h with different concentrations (0.01–1 mg mL−1) of the extracts. The mean concentrations (0.1 and 0.5 mg mL−1) of the different extracts increased the phagocytic ability and respiratory activity of head kidney leukocytes. However, the mean concentrations (0.1 mg mL−1) of leaf and fruit extracts significantly decreased the peroxidase activity of leukocytes. In addition, all ethanolic okra extracts at higher concentrations (1 mg mL−1) produced a marked reduction in the viability of the DLB-1 cell line compared to the viability recorded in the control samples. In addition, ethanolic extracts used at 0.5 and 1 mg mL−1 had a significant cytotoxic effect on the viability of PLHC-1 cells. Finally, all doses of seed and leaf extracts at higher concentrations (0.5 and 1 mg mL−1) showed significant bactericidal activity on two fish pathogenic bacteria, Vibrio anguillarum and V. harveyi strains. Finally, a remarkable antioxidant activity was detected on the ethanolic extracts. All these results point to their possible use as an alternative to chemical compounds in farmed fish.